Human extinction
Human extinction is the hypothetical end of the human species, either by population decline due to extraneous natural causes, such as an asteroid impact or large-scale volcanism, or via anthropogenic destruction (self-extinction), for example by sub-replacement fertility.
"Omnicide" redirects here. For other uses, see Omnicide (disambiguation).
Some of the many possible contributors to anthropogenic hazard are climate change, global nuclear annihilation, biological warfare, weapons of mass destruction, and ecological collapse. Other scenarios center on emerging technologies, such as advanced artificial intelligence, biotechnology, or self-replicating nanobots.
The scientific consensus is that there is a relatively low risk of near-term human extinction due to natural causes.[2][3] The likelihood of human extinction through mankind's own activities, however, is a current area of research and debate.
History of thought[edit]
Early history of thinking about human extinction[edit]
Before the 18th and 19th centuries, the possibility that humans or other organisms could become extinct was viewed with scepticism.[4] It contradicted the principle of plenitude, a doctrine that all possible things exist.[4] The principle traces back to Aristotle, and was an important tenet of Christian theology.[5] Ancient philosophers such as Plato, Aristotle, and Lucretius wrote of the end of mankind only as part of a cycle of renewal. Marcion of Sinope was a proto-protestant who advocated for antinatalism that could lead to human extinction.[6][7] Later philosophers such as Al-Ghazali, William of Ockham, and Gerolamo Cardano expanded the study of logic and probability and began wondering if abstract worlds existed, including a world without humans. Physicist Edmond Halley stated that the extinction of the human race may be beneficial to the future of the world.[8]
The notion that species can become extinct gained scientific acceptance during the Age of Enlightenment in the 17th and 18th centuries, and by 1800 Georges Cuvier had identified 23 extinct prehistoric species.[4] The doctrine was further gradually undermined by evidence from the natural sciences, particularly the discovery of fossil evidence of species that appeared to no longer exist, and the development of theories of evolution.[5] In On the Origin of Species, Darwin discussed the extinction of species as a natural process and a core component of natural selection.[9] Notably, Darwin was skeptical of the possibility of sudden extinction, viewing it as a gradual process. He held that the abrupt disappearances of species from the fossil record were not evidence of catastrophic extinctions, but rather represented unrecognised gaps in the record.[9]
As the possibility of extinction became more widely established in the sciences, so did the prospect of human extinction.[4] In the 19th century, human extinction became a popular topic in science (e.g., Thomas Robert Malthus's An Essay on the Principle of Population) and fiction (e.g., Jean-Baptiste Cousin de Grainville's The Last Man). In 1863, a few years after Charles Darwin published On the Origin of Species, William King proposed that Neanderthals were an extinct species of the genus Homo. The Romantic authors and poets were particularly interested in the topic.[4] Lord Byron wrote about the extinction of life on Earth in his 1816 poem "Darkness", and in 1824 envisaged humanity being threatened by a comet impact, and employing a missile system to defend against it.[4] Mary Shelley's 1826 novel The Last Man is set in a world where humanity has been nearly destroyed by a mysterious plague.[4] At the turn of the 20th century, Russian cosmism, a precursor to modern transhumanism, advocated avoiding humanity's extinction by colonizing space.[4]
Probability[edit]
Natural vs. anthropogenic[edit]
Experts generally agree that anthropogenic existential risks are (much) more likely than natural risks.[16][13][17][2][18] A key difference between these risk types is that empirical evidence can place an upper bound on the level of natural risk.[2] Humanity has existed for at least 200,000 years, over which it has been subject to a roughly constant level of natural risk. If the natural risk were sufficiently high, then it would be highly unlikely that humanity would have survived as long as it has. Based on a formalization of this argument, researchers have concluded that we can be confident that natural risk is lower than 1 in 14,000 per year (equivalent to 1 in 140 per century, on average).[2]
Another empirical method to study the likelihood of certain natural risks is to investigate the geological record.[16] For example, a comet or asteroid impact event sufficient in scale to cause an impact winter that would cause human extinction before the year 2100 has been estimated at one-in-a-million.[19][20] Moreover, large supervolcano eruptions may cause a volcanic winter that could endanger the survival of humanity.[21] The geological record suggests that supervolcanic eruptions are estimated to occur on average about once every 50,000 years, though most such eruptions would not reach the scale required to cause human extinction.[21] Famously, the supervolcano Mt. Toba may have almost wiped out humanity at the time of its last eruption (though this is contentious).[21][22]
Since anthropogenic risk is a relatively recent phenomenon, humanity's track record of survival cannot provide similar assurances.[2] Humanity has only survived 78 years since the creation of nuclear weapons, and for future technologies, there is no track record. This has led thinkers like Carl Sagan to conclude that humanity is currently in a "time of perils"[23] – a uniquely dangerous period in human history, where it is subject to unprecedented levels of risk, beginning from when humans first started posing risk to themselves through their actions.[16][24]
Risk estimates[edit]
Given the limitations of ordinary observation and modeling, expert elicitation is frequently used instead to obtain probability estimates.[25]